How do I change the interpolation of Nurbs curve so its Bezier?
To change a Nurb to Bezier:

Select your curve, go in Edit mode, and in the T panel (on the left of your 3D view) > Tools > press the Set Spline Type button and choose Bezier.

It looks like it doesn't work everytime so here is a way: Select your nurb in Object mode and convert it into a mesh with alt C > Mesh From Curve. Then convert this mesh again alt C Curve from Mesh. Now it's a Bezier. As you can see in Edit mode it has a lot of vertices. To simplify, activate the Simplify Curves addon, then select your curve in Object mode and Spacebar > Simplify Curves. Now in the bottom of the left panel (T) play with the Distance Error factor to reduce the amount of vertices. Once it looks good, come back in Edit mode to check out. 

To make an object follow a path:


In Edit mode make sure that your Bezier curve goes in the right direction, if not W > Switch Direction.
Put your object at the center of the scene (alt G).
Give it a Follow Path constraint. Choose the curve as Target. Click on the Animate Path button of the modifier. Now the object follows the path.
As the speed is not the one you want you need to delete the curve's self-generated animation: Select the curve, open the Graph Editor, on the left menu unfold the menu until you see Evaluation Time, select it.
Click N to display the right menu, select the Modifiers tab, click X to close the Modifiers > Generator. Now your object isn't animated anymore, but you're going to fix it manually.
Keep the curve selected. In the Properties panel > Data > Path Animation, keep the option enabled. With Frames choose the number of segments that will divide the curve. With Evaluation Time you will decide at what segment of the curve the object will be at the moment you want on the Timeline.
Now open your Timeline, put your cursor at frame 1, play with the Evaluation Time until the object is at the position you want, then insert a Keyframe on the Evaluation Time. Change the position of your cursor along the Timeline and repeat the operation. As you see you can move the object along the curve at the speed you want, you can even make it go backward. In the Graph Editor you can also change the Interpolation type (press T) so that the movements are more or less flexible.